Vendor the Shockolate engine and build it via a Docker image with every

dependency (SDL2, SDL2_mixer, fluidsynth-lite, a MIDI soundfont)
prebuilt, so compiling the engine needs no network access - just the
image and the engine source. Add res/assets/extract_assets.sh to pull
the game's data files out of a purchased GOG installer, and a Makefile
that assembles a runnable dist/ from the two.

Also add `make package`, which builds a redistributable tarball that
omits the proprietary game assets (shipping res/GET_ASSETS.txt instead)
plus license information for both the MIT tooling and the GPLv3 engine,
and a Gitea Actions workflow that builds and publishes it to
dl.ladkau.de on every push.

engine/src/GameSrc/mainloop.c

@@ -0,0 +1,172 @@
+/*
+
+Copyright (C) 2015-2018 Night Dive Studios, LLC.
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+/*
+ * $Source: r:/prj/cit/src/RCS/mainloop.c $
+ * $Revision: 1.42 $
+ * $Author: xemu $
+ * $Date: 1994/11/09 02:09:05 $
+ */
+
+/*
+ * Citadel main loops
+ *
+ * The idea here is that we have a separate loop for each game mode/setup
+ * There is a 4/12 bit change flag which is 4 global and 12 local
+ * The global loop checks OS and input
+ * Then calls the local loop, which does it's internal inlined functions
+ *  and then processes it's change flags
+ * The global loop then gets control and does it's own change flags
+ * If you want to switch modes/loops you call change_loop which both sets
+ *  global change bit 3 as well setting some variables.  When the main loop
+ *  reaches the bottom it triggers on change bit 3 and calls the switch code
+ */
+
+#define __MAINLOOP_SRC
+
+#include <stdio.h>
+
+#include "InitMac.h"
+#include "Shock.h"
+#include "amaploop.h"
+#include "cutsloop.h"
+#include "game_screen.h"
+#include "fullscrn.h"
+#include "loops.h"
+#include "fullamap.h"
+#include "input.h"
+#include "sdl_events.h"
+#include "setup.h"
+#include "status.h"
+#include "tickcount.h"
+#include "tools.h"
+#include "wrapper.h"
+
+// how is the game doing, anyway, set to true at end of time
+uchar cit_success = FALSE;
+
+// are we "paused"
+uchar game_paused = FALSE;
+
+frc *_current_fr_context;
+short _current_loop = SETUP_LOOP; /* which loop we currently are */
+short _current_3d_flag = DEMOVIEW_UPDATE;
+LGRegion *_current_view = NULL;
+uint _change_flag = 0;   /* change flags for loop */
+uint _static_change = 0; /* current static changes */
+short _new_mode = 0;     /* mode to change to, if any */
+short _last_mode = 0;    /* last mode, if you want to change back to it */
+uchar time_passes = TRUE;
+uchar saves_allowed = FALSE;
+uchar physics_running = TRUE;
+uchar ai_on = TRUE;
+uchar anim_on = TRUE;
+uchar player_invulnerable = FALSE;
+uchar player_immortal = FALSE;
+uchar always_render = FALSE;
+uchar pal_fx_on = TRUE;
+
+// Note that in the shipping version, the edit_loop stuff should never
+// get called, but needs to be SOMETHING as a place holder
+// void
+// (*citadel_loops[])(void)={game_loop,game_loop,game_loop,game_loop,setup_loop,game_loop,cutscene_loop,game_loop,automap_loop};
+// void
+// (*enter_modes[])(void)={screen_start,fullscreen_start,screen_start,screen_start,setup_start,screen_start,cutscene_start,fullscreen_start,amap_start};
+// void (*exit_modes[])(void)={screen_exit,fullscreen_exit,screen_exit,
+// screen_exit,setup_exit,screen_exit,cutscene_exit,fullscreen_exit,amap_exit};
+
+void (*citadel_loops[])(void) = {game_loop, game_loop, game_loop, game_loop, setup_loop, game_loop, cutscene_loop, game_loop, automap_loop};
+void (*enter_modes[])(void) = {screen_start, fullscreen_start, NULL, NULL, setup_start, NULL, cutscene_start, fullscreen_start, amap_start};
+void (*exit_modes[])(void) = {screen_exit, fullscreen_exit, NULL, NULL, setup_exit, NULL, cutscene_exit, fullscreen_exit, amap_exit};
+
+void loopmode_switch(short *cmode) {
+#ifdef SVGA_SUPPORT
+    extern uchar wrapper_screenmode_hack;
+#endif
+
+    // Actually switch mode
+    _last_mode = *cmode;
+    (*exit_modes[_last_mode])();
+    *cmode = _new_mode;
+    _static_change = 0;
+    if (*cmode >= 0)
+        (*enter_modes[*cmode])();
+
+#ifdef SVGA_SUPPORT
+    if (wrapper_screenmode_hack) {
+        wrapper_start(screenmode_screen_init);
+    }
+#endif
+}
+
+void loopmode_exit(short loopmode) {
+    if (exit_modes[loopmode])
+        (*exit_modes[loopmode])();
+}
+
+void loopmode_enter(short loopmode) { (*enter_modes[loopmode])(); }
+
+extern void MousePollProc(void);
+void mainloop(int argc, char *argv[]) {
+    while (_current_loop >= 0 && gPlayingGame) {
+        gShockTicks = TickCount();
+
+        if (!(_change_flag & (ML_CHG_BASE << 1)))
+            loopLine(ML | 1, input_chk()); // go get the UI stuff going
+
+        // DG: at the beginning of each frame, get all the events from SDL
+        pump_events();
+
+        // Run the loop
+        (*citadel_loops[_current_loop])();
+
+        if (globalChanges) // really, only loopmode_switch (the <<3 case)
+        {                  // will be in the game
+            // if (_change_flag&(ML_CHG_BASE<<0)) { loopLine(ML|0x10,loop_debug()); }
+            if (_change_flag & (ML_CHG_BASE << 3)) {
+                loopLine(ML | 0x13, loopmode_switch(&_current_loop));
+            }
+            chg_unset_flg(ML_CHG_BASE << 3);
+        }
+#ifdef ALWAYS_SHOW_FR
+        fr_show_rate(-1);
+#endif
+        // OR in the static change flags...
+        chg_set_flg(_static_change);
+
+        MousePollProc(); // update the cursor, was 35 times/sec originally
+
+        status_bio_update();
+        ZoomDrawProc(FALSE); //draw zoom rectangle if enabled; if not, returns immediately
+
+        SDLDraw();
+
+        ZoomDrawProc(TRUE); //erase zoom rectangle if enabled; if not, returns immediately
+    }
+
+    cit_success = TRUE;
+    // hit them atexit's
+}
+
+errtype static_change_copy() {
+    if (always_render)
+        chg_set_sta(_current_3d_flag);
+    else
+        chg_unset_sta(_current_3d_flag);
+    return (OK);
+}